1. Field of the Invention
The present invention relates to a high temperature gate valve, for example, having a disc-shaped valve element.
2. Description of the Related Art
Conventionally, a high temperature gate valve of this type includes a valve element (gate) 103 for opening and closing a flow path 102 and a guide device 104 for guiding the valve element 103 in an opening/closing direction Q provided in a valve body 101, as shown in FIGS. 10 and 11 for example. The valve body 101 includes a valve body main portion 105 and a bonnet portion 106 formed on an outer periphery of the valve body main portion 105.
The guide device 104 is formed by four guide rails 108. Each of the guide rails 108 is an elongate single member extending in the opening/closing direction Q, and fixed to an inner wall of the valve body 101 by welding. The welded portion 109 of the guide rail 108 is formed along the entire length of the guide rail 108.
In accordance with the above-mentioned structure, the valve element 103 retracts into the bonnet portion 106 when the valve element 103 moves to a fully-opened position such that a fluid 110 flows from an upstream side to a downstream side through the flow path 102. In this case, part of the fluid 110 flows into the bonnet portion 106 from inside of the valve body main portion 105. When the valve element 103 moves to a fully-closed (shut-off) position S, the flow path 102 is blocked by the valve element 103.
When the valve element 103 moves from the fully-opened position to the shut-off position S, nitrogen gas is injected into the bonnet portion 106 from outside such that the fluid 110 is pushed out from inside the bonnet portion 106 to the valve body main portion 105 and the bonnet portion 106 is filled with the nitrogen gas. Since the pressure of the nitrogen gas is higher than that of the fluid 110, the fluid 110 is prevented from entering the bonnet portion 106 from the upstream side of the valve element 103. Thus, the fluid 110 would not leak into the downstream side of the valve element 103 from the upstream side of the valve element 103 by circumventing it through the bonnet portion 106.
Since the valve element 103 is guided by the guide rail 108, vibration of the valve element 103 can be prevented when the valve element 103 moves along the opening/closing direction Q. For example, Japanese Utility Model Registration No. 2589344 (Y) describes such a high temperature gate valve 111.